In-situ microbial oxygen generation and hydrocarbon conversion in a hydrocarbon containing formation

ABSTRACT

A method for in-situ microbial oxygen generation in an underground hydrocarbon containing formation comprises: injecting into the formation an oxygen generating composition comprising thermophilic chlorate reducing micro-organisms, such as bacteria of the genus  Archaeoglobus, Geobacillus  and/or  Thermus , which multiply at a temperature of at least 60° C.; and inducing the multiplied micro-organisms to convert the hydrocarbons and/or other pore fluid components in-situ into transportable or disposable products

BACKGROUND OF THE INVENTION

The invention relates to a method for in-situ oxygen generation in ahydrocarbon containing formation.

Such a method is known from U.S. Pat. No. 5,163,510.

The method known from this prior art reference comprises:

injecting into the formation a fluid comprising a source of oxygen thatchemically releases oxygen into the formation;

inducing micro-organisms present in the formation to multiply using theoil as their carbon source and the chemically produced oxygen in theinjection water as their oxygen source; and

allowing the multiplied micro-organisms to convert oil from theenvironment.

In this known method the source of oxygen is provided by injecting watercomprising an oxidizing compound selected from the group consisting ofH₂O₂, NaClO₃, KClO₄, NaNO₃ and combinations thereof, which are assumedto be chemically converted to result in oxygen. This assumption is basedon the fact that oxygen generation from Microbial Chlorate Reduction wasfor the first time reported in 1996 by van Ginkel at al in 1996,Archives of Microbiology 166:321-326.

In accordance with the teachings of U.S. Pat. No. 5,163,510 thechemically generated oxygen is then used by microbes to converthydrocarbons.

Limitations of the use of the known oxidizing compounds known from U.S.Pat. No. 5,163,510 for chemical oxygen generation are that H₂O₂ maydissociate during or shortly after the injection process, and thatchemical conversion of NaNO₃, NaClO₃ and KClO₄ do not generate oxygen attemperatures lower than 120° Celsius.

Moreover, the microbes Pseudomonas putida, Pseudomonas aeruginosa,Corynebacterium lepus, Mycobacterium rhodochrous and Mycobacteriumvaccae disclosed in U.S. Pat. No. 5,163,510 are non-thermophilicmicro-organisms, which are unable to reduce chlorate and/or multiply attemperature of at least 60° C. This will prevent the method known fromU.S. Pat. No. 5,163,510 to be beneficial for application throughout anentire hydrocarbon containing formation as the ambient temperature in ahydrocarbon containing formation often exceeds 60° C.

The use of microbial chlorate reduction as mechanism for in-situ oxygengeneration and thereby stimulating microbial activity using hydrocarbonsas carbon and energy source has been reported for the bioremediation ofhydrocarbon spills at ambient atmospheric temperatures in the followingprior art references:

-   Coates et al., 1998, Nature 396(6713): 730-   Coates et al., 1999, Applied Environmental Microbiology 65(12):    5234-5341-   Coates et al., 2004, US patent 2004/0014196A1, which prior art    references are collectively referred to as Coates et al (1998, 1999,    2004)-   Tan et al., 2006, Biodegradation 17(1): 113-119-   Mehboob et al., 2009: Applied Microbiology and Biotechnology 83(4):    739-747-   Langenhoff et al., 2009, Bioremediation Journal, 13(4): 180-187

There is a need to provide an method for in-situ thermophilic microbialoxygen generation wherein a controlled amount of oxygen ismicrobiologically produced in-situ deeper in the hydrocarbon containingformation where the temperature is at least 60° C.

There is furthermore a need to provide an enabling process for thestimulation of in-situ thermophilic microbial conversion of hydrocarbonswherein oxygen is microbiologically produced from the injected oxygensource only at high temperature locations in a hydrocarbon containingformation where injected or indigenous micro-organisms encounter theinjected electron acceptor in addition to an electron donor, such ashydrocarbons, volatile fatty acids, etc.

There is also a need for a method for thermophilic microbial oxygengeneration through chlorate reduction at the oil water interface, incontrast to chemical generation of oxygen known from U.S. Pat. No.5,163,510 that can also occur in oil-poor parts of the reservoir.

Utilization of microbes to enhance hydrocarbon recovery is hampered bythe limited bioavailability and biodegradability of the hydrocarbonsunder hot reservoir conditions.

Thus there is also a need to provide a way to improve bioavailabilityand biodegradability in hot hydrocarbon containing formations where theambient temperature is at least 60° C.

SUMMARY OF THE INVENTION

In accordance with the invention there is provided a method for in-situoxygen generation in an underground hydrocarbon containing formation,the method comprising injecting into the formation an oxygen generatingcomposition which releases oxygen (O₂) by reduction of chlorate (ClO₃—),wherein:

the formation has a temperature of at least 60° C.;

the composition comprises thermophilic chlorate reducingmicro-organisms, which multiply at an ambient temperature of at least60° C.; and

the multiplied thermophilic chlorate reducing micro-organisms convertthe hydrocarbons and/or other pore fluids in-situ into transportable ordisposable products.

In an embodiment the thermophilic chlorate reducing micro-organismscomprise bacteria of the genus Archaeoglobus, Geobacillus and/or Thermusand use hydrogen (H) and electrons (e) provided by hydrocarbons,volatile fatty acids and/or other pore fluids in the formation followedby dismutation of chlorite (ClO₂ ⁻) by the micro-organisms on the basisof the reactions:

ClO₃ ⁻+2H⁺+2e->ClO₂ ⁻+H₂O

ClO₂ ⁻->Cl⁻+O₂

In a suitable embodiment the thermophilic chlorate reducingmicro-organisms multiply at an ambient temperature of at least 80° C.and comprise bacteria of the genus Archaeoglobus fulgidis.

Optionally, the method according to the invention furthermore comprises:

injecting into the formation an oxygen generating composition, whichcomprise or generates chlorate in the formation and which releasesoxygen (O₂) by thermophilic microbial reduction of chlorate (ClO₃ ⁻) bythe micro-organisms, using hydrogen (H) and electrons (e) provided bythe hydrocarbons, volatile fatty acids and/or other pore fluidcomponents, such as oil & gas contaminants such as H₂S, thiophenes andmercaptanes, followed by dismutation of chlorite (ClO₂ ⁻) bymicro-organisms on the basis of the reactions:

ClO₃ ⁻+2H⁺+2e->ClO₂ ⁻+H₂O

ClO₂ ⁻->Cl⁻+O₂;

inducing multiplication of the thermophilic chlorate-reducingmicro-organisms (Archaeoglobus, Geobacillus, Thermus), otherchlorate-reducing thermophilic micro-organisms and other micro-organismsthat can use the hydrocarbons, volatile fatty acids and/or other porefluid components (e.g. oil & gas contaminants as H₂S, thiophenes andmercaptanes) as their carbon source and/or electron donor and theinjected composition or the oxygen generated by thermophilic chloratereduction thereby as their electron acceptor and/or oxygen source; and

inducing the multiplied micro-organisms to convert the hydrocarbonsand/or other pore fluid components in-situ into transportable products,such as in Microbial Enhanced Oil Recovery (MEOR) and/or ECBM EnhancedCoal Bed Methane (ECBM) processes.

The multiplied thermophilic micro-organisms generated in accordance withthe method according to present invention may be used for in-situconversion of coal, shale oil, oilshale, bitumen and/or a viscous crudeoil into a synthetic crude oil with a reduced viscosity and/or toconvert associated contaminants, such as H₂S, thiophenes andmercaptanes, into oxidized sulfur fractions that remain within thereservoir brine.

The method according to the invention may be used to improvebioavailability and biodegradability of hydrocarbons at thermophilic(60-120° C.) & anaerobic conditions in underground formations containinghydrocarbons, volatile fatty acids and other pore fluid components andmicro-organisms, by the process of Thermophilic Microbial ChlorateReduction. The process will generate oxygen in-situ that will enhancebioavailability and biodegradability, which subsequently will enablesenhanced recovery of hydrocarbons (of improved quality) via otherprocess like Microbial Enhanced Oil Recovery (MEOR), Microbial EnhancedCoalbed Methane (MECBM) or pretreatment of heavy hydrocarbon crudes(heavy oil, bitumen) prior to processes as Steam Assisted GravityDrainage (SAGD).

The oxygen generating composition may comprise perchlorate (ClO₄—) fromwhich chlorate (ClO₃—) is generated using electrons released byhydrocarbons, volatile fatty acids and/or other pore fluid components(e.g. oil & gas contaminants as H₂S, thiophenes and mercaptanes) aselectron donor on the basis of the following reaction:

ClO₄ ⁻+2H⁺+2e->ClO₃ ⁻+H₂O.

The hydrocarbons may comprise viscous crude oil, coal and/or other longchain hydrocarbons and the micro-organisms may comprise thermophilic(per)chlorate-reducing bacteria or archaea, such as archaea and bacteriaof the genus Archaeoglobus, Geobacillus, Thermus and/or otherthermophilic genera able to reduce chlorate and convert fatty acids orlong chain hydrocarbons into short chain hydrocarbons being indigenousto the formation or introduced by injection.

The other pore fluid components may comprise fatty acids, natural gascontaminants; H₂S, thiophenes, and mercaptanes, in which case themicro-organisms may comprise archaea and bacteria of the genusArchaeoglobus, Sulfolobus, Ferroglobus, Thiobacillus, Thiomicrospira orother genera able to convert natural gas contaminants.

These and other features, embodiments and advantages of the methodaccording to the invention are described in the accompanying claims,abstract and the following detailed description of a non-limitinghypothetical example.

The present invention novelty compared to the inventions previouslyreported resides in:

Providing a microbial chlorate-reducing and oxygen-generating process(i.e. different from the invention of U.S. Pat. No. 5,163,510, in whichoxygen is assumed to be chemically produced (not by chlorate-reducingmicroorganisms) and only assumes microbial utilization of oxygen);

Providing such microbial chlorate-reducing and oxygen-releasing processthat can operate at high temperatures in the range from 60° C. up to120° C. relevant to hydrocarbon containing reservoirs. The microbialmethod according to the invention can operate at an elevated temperatureof at least 60° C. and is therefore different from the bioremediationmethod disclosed in US patent application 2004/0014196 A1 (Coates),which releases oxygen at temperatures <40° C. and the method known fromU.S. Pat. No. 5,163,510 that enables the use of micro-organisms at atemperature below 60° C. (but not higher) and therefore seriously limitsthe application of the known method in hot hydrocarbon containingformations.

The thermophilic microbial chlorate-reducing and oxygen-releasing methodaccording to the invention enhances bioavailability and biodegradabilityof hydrocarbons, which subsequently enables enhanced recovery ofupgraded hydrocarbons from hydrocarbon containing formations optionallyby:

a) enhanced oil recovery from oil bearing formations (MEOR),b) enhanced methane production of coal reservoirs (ECBM),c) pretreatment of heavy oil deposits before SAGD operation; andd) in-situ conversion of oil and natural gas contaminants; H₂S,thiophenes and mercaptanes, which conversion involves decontamination ofhydrocarbons and is therefore different from US patent 2004/0014196A1,which aims to bioremediate hydrocarbons in a shallow low temperatureenvironment or U.S. Pat. No. 5,163,510, which aims to stimulate MEORonly.

The method according to the invention generates oxygen in-situ that willenhance bioavailability and biodegradability, which subsequently willenable enhanced recovery of hydrocarbons (of improved quality) via otherprocess like Microbial Enhanced Oil Recovery (MEOR), Microbial EnhancedCoalbed Methane (MECBM) or pretreatment of heavy hydrocarbon crudes(heavy oil, bitumen) prior to processes as Steam Assisted GravityDrainage (SAGD). The process can also enable in-situ natural gascontaminant removal resulting in upgraded hydrocarbons. The inventionshould therefore be considered as a strong enabling process for othersubsurface thermophilic microbial processes.

When used in this specification and claims the term thermophilicchlorate reducing micro-organisms means that these micro-organismsmultiply at an ambient temperature of at least 60° C.

These and other features, embodiments and advantages of the methodaccording to the invention are described in the accompanying claims,abstract and the following detailed description of non-limitingembodiments depicted in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows the consumption of lactate as an electron donor andconversion of chlorate to chloride at 85° C. by the thermophilicArchaeoglobus fulgidus DSM4139 microorganism in laboratory experimentthat demonstrates the viability of the method according to the inventionat an elevated temperature.

DETAILED DESCRIPTION OF THE DEPICTED EMBODIMENT

FIG. 1 shows the results of a laboratory experiments which demonstratedthat Archaea from the genus Archaeoglobus can perform chlorate reductionat temperatures up to 85-95° C.

Archaeoglobus have often been encountered in hydrocarbon containing hightemperature reservoirs as evident from molecular and cultivationexperiments. Moreover, members of this genus have been shown to be ableto convert fatty acids and alkanes. Members of this genus therefore areone of the most relevant candidates for the thermophilic microbialchlorate-reduction process.

FIG. 1 illustrates the results of a laboratory experiment in whichlactate was consumed as electron donor and chlorate was converted intochloride at 85° C. by the micro-organism comprising bacteria of thegenus Archaeoglobus fulgidus DSM4139.

It is observed that thermophilic microbial (Per)Chlorate Reduction at atemperature of at least 60° C. has never been described in the prior artfor hot hydrocarbon containing environments with fatty acids orhydrocarbons as electron donor and that the experiment revealed thatbacteria of the genus Archaeoglobus fulgidus DSM4139 will have anunexpectedly good performance for thermophilic microbial (Per)ChlorateReduction in a hot hydrocarbon containing formation at an ambienttemperature of at least 60° C.

Example

A suitable embodiment of the method according to the invention,comprises the following steps:

a) Screening whether a target underground crude oil and/or natural gascontaining reservoir formation has features, such as temperature,salinity, heterogeneity, oil characteristics, micro-organisms, volatilefatty acids, hydrogen ions, acetate, propionate or butyrate and/or otherpotential electron donors, etc., which allow use of the method accordingto the invention;b) Analyzing the composition of the water, oil and/or natural gas in theformation, for example by screening a sample taken from the formation;c) Identification of potentially interesting micro-organisms withmolecular DNA technologies using either general (16S rRNA-related)primer sets or enzyme/functional group specific primer sets(nitrate/nitrite-reductase, (per)chlorate reductases, chloritedismutase, or hydrocarbon (alkane) degrading enzymes or usingmetagenomics;d) Isolation of potentially interesting indigenous microbes fromavailable core, formation water, and oil samples using VFA's (acetate,proprionate, butyrate, etc.), hydrocarbon components (e.g. long chainalkanes) or typical gas contaminants (e.g. H₂S) as electron donor andnitrate, oxygen or perchlorate, chlorate or chlorite as electronacceptor.e) Determination of the optimal nutrient mix (electron donor, N/Pnutrient, trace elements, SRB-inhibiting chemicals, etc.) using theidentified and/or cultivated micro-organisms;f) Microbial incubations using the potential successful nutrientcompositions and gas contaminants, VFA's or oil components (e.g. longchain alkanes) to prove microbial activity on lab scale;g) Optional middle phase could be to verify chance of success by coreflood experiments; ande) The following actual chemical injection and in-situ conversionprocedure:e1) Shut-in and clean-up of a near wellbore area of the crude oil, tarsand, shale oil, natural gas and/or other hydrocarbon containingreservoir formation (either chemically or by flushing);e2) Injection of microbial cultures (single species or consortia derivedfrom enrichments inoculated with production fluids from the treatedreservoir) into the formation to boost the required indigenous microbialspecies;e3) Injection of optimized nutrient mixture (main components being:oxygen, perchlorate and or chlorate and/or nitrate possibly continuouslybut more likely push-wise to avoid the development of achlorate-utilizing biofilm limited to the wellbore to ensure deepplacement into the reservoir formation and thereby stimulating therequired indigenous microbial community; ande4) Monitoring of the in-situ conversion method according to theinvention based on increase in oil production, change in water-cut,change in produced oil and/or natural characteristics and/orcomposition, detection of target micro-organism(s) using molecular DNAtechnologies and/or cultivation dependent screening.

1. A method for in-situ oxygen generation in an underground hydrocarboncontaining formation, the method comprising injecting into the formationan oxygen generating composition which releases oxygen (O₂) by reductionof chlorate (ClO₃—), wherein: the formation has a temperature of atleast 60° C.; the composition comprises thermophilic chlorate reducingmicro-organisms which multiply at an ambient temperature of at least 60°C.; and the multiplied thermophilic chlorate reducing micro-organismsconvert the hydrocarbons and/or other pore fluids in-situ intotransportable or disposable products.
 2. The method of claim 1, whereinthe thermophilic chlorate reducing micro-organisms comprise bacteria ofthe genus Archaeoglobus, Geobacillus and/or Thermus, which use hydrogen(H) and electrons (e) provided by hydrocarbons, volatile fatty acidsand/or other pore fluids in the formation followed by dismutation ofchlorite (ClO₂ ⁻) by the micro-organisms on the basis of the reactions:ClO₃ ⁻+2H⁺+2e->ClO₂ ⁻+H₂OClO₂ ⁻->Cl⁻+O₂
 3. The method of claim 2, wherein the thermophilicchlorate reducing micro-organisms multiply at an ambient temperature ofat least 80° C. and comprise bacteria of the genus Archaeoglobusfulgidis.
 4. The method of claim 1, wherein the oxygen generatingcomposition comprises perchlorate (ClO₄) from which chlorate isgenerated using electrons released by the volatile fatty acids,hydrocarbons or other pore fluid components as electron donor on thebasis of the following reaction:ClO₄ ⁻+2H⁺+2e->ClO₃ ⁻+H₂O.
 5. The method of claim 4, wherein thehydrocarbons comprise viscous crude oil and/or other long chainhydrocarbons and the bacteria comprise crude oil degrading aerobicbacteria, such as bacteria of the genus Geobacillus, Thermus and/orother bacteria that convert long chain hydrocarbons into short chainhydrocarbons being indigenous to the formation of introduced byinjection.
 6. The method of claim 5, wherein the multiplied bacteriadissociate crude oil from the formation by microbial dismutation ofchlorite for the partial biotic and abiotic aerobic conversion of oil.7. The method of claim 5, wherein the multiplied bacteria dissociateviscous crude oil from the formation by microbial dismutation ofchlorite for the partial biotic and abiotic aerobic conversion of oiland the method is used to enhance crude oil recovery from the formation.8. The method of claim 1, wherein the other pore fluids comprise naturalgas contaminants, such as CO₂ and/or H₂S, and the micro-organismscomprise bacteria of the genus Sulfolobus, Ferroglobus, Thiobacillus,Thiomicrospira or other genera able to convert natural gas contaminants.9. The method of claim 8, wherein the formation comprises a H₂Scontaining pollutant from which the oxygen generates more oxidizedsulfur compounds like elemental sulfur, poly sulfide, poly thionates andH₂SO₄.
 10. The method of claim 1, wherein the other pore fluidcomponents comprise hydrogen ions, acetate, propionate or butyrateand/or other volatile fatty acids and the injected chemical comprisesperchlorate, chlorate and/or chlorite and another chemical, which canserve as electron acceptor or oxygen source, such as oxygen, nitrate,nitrite and hydrogen peroxide in order to ensure deep placement of theperchlorate, chlorate and/or chlorite into the formation.
 11. The methodof claim 10, wherein composition is injected either continuously orpulse-wise into the formation to ensure deep placement of the nitrate,nitrite, oxygen, perchlorate, chlorate or alternative electron acceptorsinto the formation.
 12. The method of claim 1, wherein themicro-organisms are bacteria that are either indigenous to the formationand/or introduced by injection into the formation.
 13. The method ofclaim 1, wherein the micro-organisms comprise a single speciesmicroorganism or a mixture and/or consortia of micro-organisms.
 14. Themethod of claim 1, wherein the micro-organisms are after a period oftime substituted by single or multiple enzyme samples that can be watersoluble or added as immobilized structures, such as bio-nano particlesand/or the micro-organisms are either present in or introduced into theformation as highly active microbes or as spores, cysts or encapsulatedmicro-organisms.
 15. The method of claim 1, wherein the micro-organismseither perform the microbial conversion of perchlorate via chlorate andchlorite to chloride and oxygen (or parts thereof) or the microbialconversion of hydrocarbons or natural gas contaminants or microorganismthat comprise both the perchlorate/chlorate/chlorite as well as thehydrocarbon conversion/natural gas contaminant conversion activity,and/or the micro-organisms contain key enzymes from a nitrate-reductionand/or chlorate-reduction pathway such as perchlorate reductase,chlorate reductase, chlorite dismutase, nitrate reductase or nitratereductase or combinations thereof.